In elevator equipment, it is essential that the landing entrances at any floor not open until the elevator car has arrived at that floor.
Similarly, it cannot receive the order to leave that floor until the landing entrance is closed, and closed correctly.
To this end, conventional practice encompasses the use of a positive safety lock with dual bolts, whose operation will now be described.
This type of conventional lock comprises:
a housing which can be attached to the door frame of a landing entrance;
a door-locking bolt arranged in a sliding configuration in the housing and acted upon by a compression spring, this bolt being capable of working in conjunction with a stationary striking pin attached to the leaf of a swinging or sliding door acting on a safety mechanism associated with the bolt and capable of allowing the total release of the locking bolt, provided that all of the parameters relating to the closing of the door are brought together;
a bolt-control lever linked to the bolt and actuated in a swinging motion around a pin, so as to cause the translational movement of the bolt during opening and closing;
a lever-operating arm acting directly on its axis in a position facing the housing, or by means of an angled retransmission system into a position to the side of the housing, this operating lever being mounted on the housing in such a way that it can be actuated in a frontal or lateral plane by a stationary or mobile cam fastened to an elevator car;
an electrical bolt contact ensuring closing only when the bolt is completely released in the locking configuration, and permitting, in this position only, the operation of the elevator;
secondarily, an electrical contact indicating the presence of the elevator car which closes the entrance when the operating arm is completely pushed back by the stationary or mobile cam attached to the car, and corresponding to an integral retraction of the bolt;
a pull-away electrical contact whose short-circuiting element is attached to the leaf of the door, so as to allow the operation of the elevator car cam only if the door is closed;
an electrical cable-bushing device for the cables emanating from the different electrical contacts;
means for attaching the housing.
This type of lock, widely used today in the sphere of application mentioned above, gives good results, but has the major disadvantage of requiring a very large range of models in order to address market requirements, based on all of the situations encountered.
Indeed, each of these cases calls for a special application for the lock, thereby engendering its specific design parameters.
By way of example, the most frequently-encountered cases include the following:
exit of the bolt to the right or left as a function of the direction in which the door opens;
the length of the different bolts, depending on the distance of the post of the door frame to which the lock is attached from the door;
the placement of the pull-away/presence contact to the right or left, or to the outside of the lock;
the positioning of the bevelled edge of the bolt as a function of the direction in which the door is opened and of the mode of operation, i.e., swinging, sliding, guillotine, etc;
the positioning of the control lever depending on whether the bolt is on the right or left;
the frontal, exterior, or lateral position of the operating arm as a function of the cam in the elevator car;
the position of the bolt and car-presence contacts.
It will easily be understood that this diversity of locks is very difficult to deal with, from both the manufacturing and the installation standpoints.
As regards installation, not only does the installer have to bear the excess cost arising from the limited production of each type of lock, but, moreover, the installer must keep a large inventory in order to be able to deal with immediate demand. This last point is also important from a financial perspective, since it entails a costly investment required for distribution of inventories difficult to control.